Tensioning device for a strapping device

ABSTRACT

The present disclosure relates to a tensioning device of a strapping device for strapping packaged material with a strap. The tensioning device includes a tensioning wheel operatively connectable to a drive device to rotate the tensioning wheel about a rotational axis. The tensioning wheel has a circumferential surface configured to engage the strap. The tensioning device also includes a movable spacer provided on the tensioning wheel in the region of the circumferential surface of the tensioning wheel. The spacer is movable between a first position in which part of the spacer is a first distance from the rotational axis and a second position in which the part of the spacer is a second different distance from the rotational axis. The spacer projects beyond the circumferential surface of the tensioning wheel in at least one of the positions.

This application is a national stage entry of PCT/CH2015/000013, filedon Feb. 10, 2015, which claims priority to and the benefit ofSwitzerland Patent Application Nos.: (1) 183/14, filed on Feb. 10, 2014;(2) 182/14, filed on Feb. 10, 2014; and (3) 181/14, filed on Feb. 10,2014, the entire contents of each of which are incorporated herein byreference.

The present disclosure relates to a tensioning device of a strappingapparatus for the strapping of packaged articles with a strapping band,in particular with a plastics strapping band, which is equipped with atensioning wheel which is operatively connected or operativelyconnectable to a drive device to set the tensioning wheel in arotational movement about an axis of rotation, wherein the tensioningwheel has a circumferential surface which is designed for engaging intothe strapping band. In the context of the present disclosure, thetensioning device may be provided both for static strapping apparatusesand for mobile, in particular portable, strapping apparatuses.

Strapping apparatuses of said type may be formed inter alia as a staticinstallation which is utilized for equipping relatively large packagedarticles, or multiple individual packaged articles placed together toform a packaged article unit, with one or more band straps. The bandstraps are normally formed from a band which is drawn from a supply rolland laid as a ring-shaped strap around the packaged article. For thispurpose, the strapping band is shot with its free end first into achannel of the strapping apparatus, which channel surrounds the packagedarticle, with a spacing, in the manner of a portal or in ring-shapedfashion. Normally, as soon as the band end has reached a particularpoint in the channel, the band end is clamped and the band is thenretracted again. As a result, the loop of the strapping band istightened and the band passes out of the channel and into contact withthe packaged article. Subsequently, a band tension is applied to theband, and the band ring is equipped with a fastening and is cut off fromthe supply roll. As strapping band, use is made both of metallic bandsand of plastics bands. The strapping apparatuses are normally adapted tothe strapping band types used therewith, in particular with regard tothe connecting device by way of which two band layers, which lie oneover the other in sections, of the strapping bands can be non-detachablyconnected to one another.

In the case of previously known solutions, during the retraction of thestrapping band, the band of the loop is generally retracted at highspeed in a direction opposite to the advancing direction in which theband was previously shot into the channel. It is normally also the casethat the tensioning wheel of the tensioning device is arranged in saidretraction path, by means of which tensioning wheel the tensioningprocess is only subsequently performed. Since the tensioning wheel isnormally not driven, and is thus at a standstill, during the retractionprocess, there is the risk of the strapping band being guided or pulledover the tensioning wheel during the band retraction movement. As aresult of the contact and the relative movement between the tensioningwheel and the strapping band, the strapping band can be damaged by thetensioning wheel. This risk is all the greater if the circumferentialsurface of the tensioning wheel is not smooth but is equipped with ageometrically defined or undefined roughened surface, such as forexample a fluting, knurling or toothing, such as is common for improvingthe engagement conditions and for the avoidance of slip in the case oftensioning wheels. As a result of such damage to the strapping bandgenerated by the tensioning wheel, the tensile strength of the strappingband can be reduced in the region of the damage, such that the bandtears under the imparted tensile stress. Further disadvantages of suchengagement can be seen in the friction-induced reduction of the bandretraction speed and in the abrasion caused by the contact of the bandwith the rough surface of the tensioning wheel during the bandretraction phase.

The present disclosure is therefore based on the object of improving astrapping device for strapping packaged articles with a strapping bandsuch that disadvantages that arise as a result of the relative speedbetween the tensioning wheel and the band during the band retractionphase are as far as possible avoided.

Said object is achieved according to the present disclosure by way of atensioning device of the type mentioned in the introduction in that, inthe region of the circumferential surface of the tensioning wheel, thereis provided on the tensioning wheel at least one movable spacer elementwhich can be arranged in a first position and in a second position thatdiffers from said first position, wherein, in the first position, thespacer element can be arranged at least in sections with a first spacingto the axis of rotation of the tensioning wheel and, in the secondposition, can be arranged with a second spacing, at least in sections,to the axis of rotation of the tensioning wheel, the first spacingdiffers here from the second spacing, and the spacer element, in atleast one of the two positions, projects beyond the circumferentialsurface of the tensioning wheel. In this context, the spacing to theaxis of rotation may be understood to mean a spacing of a region of therespective spacer element, which region which is provided for contactwith the strapping band at least in one of the two positions, to theaxis of rotation. The present disclosure thus makes it possible, by wayof the at least one spacer element which is movable relative to thetensioning wheel, for the strapping band to be prevented from cominginto contact with the surface of the tensioning wheel when the spacerelement assumes its position in which it projects at least in sectionsbeyond the circumferential surface of the tensioning wheel.

In one embodiment of the present disclosure, it may be provided that, byway of a force externally applied to the spacer element of thetensioning wheel, the spacer element can be transferred at least insections from the position with the relatively large radial spacing tothe axis of rotation into the other position with the relatively smallradial spacing to the axis of rotation. The expression “externallyapplicable” may in this case be understood in particular to mean thatthe force is applied by an element which does not belong to thetensioning wheel or to the spacer element itself, in particular by thestrapping band. The spacer element may be in the form of a passiveelement with regard to its change in position or the change in itsgeometrical shape. Since it is thus the case in such embodiments of thepresent disclosure that there is no need for a drive of the tensioningwheel to be provided for the generation of the change in position orshape of the spacer element, the tensioning wheel can be of structurallysimple form despite the realization of the function according to thepresent disclosure.

A structurally simple and nevertheless compact embodiment of the presentdisclosure may provide that the spacer element is arranged so as to berotatable together with the tensioning wheel. The at least one spacerelement may be movable relative to the tensioning wheel itself, whereinchanges in position of the at least one spacer element can take place,and are possible, in particular during a rotation of the tensioningwheel.

It may be provided that the at least one spacer element assumes itsfirst position during the band retraction phase, such that, during theband retraction phase, the strapping band is arranged against the atleast one spacer element of the tensioning wheel and thus with a spacingto the circumferential surface of the tensioning wheel. The band is thusideally prevented by the spacer element from coming into contact withthe circumferential surface of the tensioning wheel during the bandretraction phase. If such contact is not entirely avoidable, saidcontact should however at least be reduced to the greatest possibleextent by the spacer element. For the tensioning phase or the tensioningprocess, it is by contrast possible, in certain embodiments of thepresent disclosure, for the at least one spacer element to be moved withat least one of its sections into the second position thereof in which,at those points of the circumferential surface at which the tensioningwheel is looped around by the strapping band, said at least one spacerelement is arranged no higher than the same height as thecircumferential surface, or is arranged lower than said circumferentialsurface. In this way, the spacer element leaves the circumferentialsurface free for the desired contact with the circumferential surfaceduring the tensioning process.

The at least one spacer element may be arranged in differentorientations relative to the circumferential surface. Here, anorientation of the spacer element is parallel to the circumferentialdirection of the tensioning wheel. In this way, it is possible, withparticularly little outlay in terms of construction, for the function ofthe spacer element to be ensured along the entire circumference of thetensioning wheel.

As a spacer element, both passive and active spacer elements may beprovided for the purposes of moving the at least one spacer element intoits two positions. Active elements may be understood as elements whichperform a change in position or shape automatically, for exampleelements which perform self-generating changes in position and/or shapeof the spacer element through the use of hydraulic or pneumatic energyor the use of electrical or magnetic energy. By contrast, however, incertain embodiments passive spacer elements are preferred, that is tosay spacer elements which have a change in position and/or shapeexternally forcibly imparted to them, without the spacer element itselfcontributing to this. A change in position or shape may be realized forexample by way of a counterpart roller which imparts a pressure force inthe direction of the tensioning wheel and presses the band against thespacer element. In the presence of a correspondingly high forcecoordinated with the characteristics of the spacer element, it ispossible in this way for the region of the spacer element to be providedwith a smaller spacing to the axis of rotation of the tensioning wheelthan in the unloaded state. The change in spacing may be utilized to theeffect that, in the region of the counterpart roller, the strapping bandbears now not against the spacer element but against the circumferentialsurface of the tensioning wheel.

Certain embodiments of the present disclosure are in particularembodiments in which there is no need for control of the times at whichchanges in position of the spacer element are to be performed. Oneembodiment of a passive spacer element may therefore provide that theforces exerted by the band on the tensioning wheel and thus also on thespacer element are themselves utilized to perform a change in position.Here, a particularly advantageous embodiment may provide that the forcesof different magnitude during the band retraction phase and thetensioning phase are utilized to determine whether a change in positionand/or shape should be initiated. A switching process is not necessaryfor this purpose; the change in position and/or shape may be realized,and also reversed, automatically. For this purpose, the spacer elementmay be designed such that the force exerted by the band on thetensioning wheel during the band retraction phase is not sufficient tomove the spacer element into its second position. The relatively higherforces that are exerted by the band on the tensioning wheel during thetensioning process are however suitable, by way of correspondinglysuitable configuration of the spacer element, for moving said spacerelement into its second position in which contact is then realizedbetween the strapping band and the circumferential surface. In thisembodiment, neither additional energy nor monitoring or control of theprocess are necessary. An embodiment of the present disclosure which isuncomplicated in terms of construction but which is neverthelessfunctionally reliable is thus realized.

One embodiment of the present disclosure may provide both a counterpartroller, which imparts force in the direction of the tensioning wheel,and the utilization of the band for generating the change in position.In this way, it is possible for the change in position and/or shape ofthe spacer element to be realized in a particularly functionallyreliable manner. Here, it may be advantageous if, in particular at thestart of the tensioning phase, the band is forced against the spacerelement by way of a counterpart roller or some other suitable elementand, in this way, the spacer element is, at least in the region of thecounterpart roller, forced back such that the band comes into contactwith the circumferential surface. In this way, the band enters intoengagement with the tensioning wheel, whereby it is possible to commencewith increasing the band tension. As a result of this, the band beginsto lie against the spacer element over an at least substantiallypredetermined wrap angle corresponding to its provided band guidancearound the tensioning wheel. By way of an increase of the band tension,it is then also possible for the pressure force to be increased to amagnitude sufficient to force the spacer element back in the region ofcontact with the band, in such a way that the band is, over its wrapangle on the tensioning wheel, in contact with the circumferentialsurface of said tensioning wheel. Here, it is particularly advantageousfor the spacer element to be forced back to such an extent that thespacer element, at least over a part of the wrap angle (and in certainembodiments substantially over the entire wrap angle) does not projectbeyond the contact region of the circumferential surface with the band.It is thus possible for the tensioning wheel to remain in engagement byway of its non-smooth circumferential surface even in the presence offurther increasing band tension, and the band tension can be increasedup to an intended value.

In this context, the expression “do not project beyond thecircumferential surface” can also be understood to encompassarrangements in which the spacer element projects only slightly beyondthe circumferential surface, and the strapping band, for example owingto its elasticity and deformability, can come into contact with thecircumferential surface despite said small projecting length.

In another embodiment of the present disclosure, the circumferentialsurface of the tensioning wheel may, at least over a part of the lengthof the circumference, be equipped with a groove in which, as aconstituent part of the spacer element, there may be arranged a ringelement which can be arranged at least in sections in differentpositions. Here, the ring element may advantageously be arranged in afirst position, in which it is elevated at least in sections in relationto the circumferential surface, and in a second position, in which thering element, at least in sections, does not project beyond thecircumferential surface.

Basically, a multiplicity of different solutions is conceivable by wayof which the spacer element, such as for example the ring element,prevents the strapping band from coming into contact with the surface,which is intentionally kept non-smooth, of the tensioning wheel. Aparticularly advantageous solution may provide that the ring elementextends substantially over the entire circumference of the tensioningwheel and is arranged in a groove which extends over the circumferenceof the tensioning wheel. In an expedient refinement of the presentdisclosure, it may be possible for the ring element to be forced intothe groove by the strapping band under pressure loading, such that,owing to the ring element being forced back in this way, it is the casealong a wrap angle that the ring element no longer projects beyond thecircumferential surface, and the strapping band can come into contactwith the circumferential surface of the tensioning wheel. The ringelement may be designed so as to be forced back into the groove in thedescribed manner only under the action of a certain minimum force actingon the ring element. Said minimum force may be predetermined such thatit is reached during the tensioning process but not during the bandretraction process.

In a further particular advantageous embodiment, it is possible, throughutilization of resilient elasticity, for the ring element, or otherembodiments of the spacer element, to be restored immediately andautomatically when correspondingly relieved of the band pressure afterhaving previously been subjected to load. To achieve this, the ringelement, or some other embodiment of the spacer element, may itself beof resiliently elastic form. In further embodiments, there may beprovided, in addition to the possibly at least substantially rigid ornot adequately elastic spacer element, at least one resiliently elasticelement, such as for example one or more O-rings or other springelements, which impart a returning action to the spacer element. Asidefrom a high level of functional reliability, these solutions also makeit possible to avoid a supply of external energy.

Finally, in a further embodiment of the tensioning device, during thetensioning process, the tensioning wheel rotates and, in relation to apositionally static polar coordinate system of the tensioning wheel, thespacer element is forced into the groove at the at least substantiallyalways identical circumferential section of the tensioning wheel,whereas, at the remaining circumferential section, against which thestrapping band does not bear, the spacer element projects in relation tothe circumferential surface.

The above-stated object is furthermore achieved by way of a strappingdevice which is equipped with one of the tensioning devices according tothe present disclosure.

Another embodiment of the present disclosure—which may also be ofindependent significance independently of the number of wheels, rollersand motors used for the imparting of movements to the band andindependently of the design of the tensioning wheel—may provide anactuable means by which at least one wheel of a wheel pair of theadvancing device can be switched into a state in which the strappingband can be displaced between the wheel pair in a direction opposite tothe band advancement movement, without a corresponding motor drivemovement being transmitted to the strapping band. With the presentdisclosure, provision is thus made for the state of the wheel pair to bechanged from a state in which the band is clamped between said wheels,which state permits in particular the advancement of the band, into astate in which the band can move through between the wheel pairregardless of a driven movement of a wheel of the wheel pair. Accordingto the present disclosure, the clamping state between the wheel pair,which clamping state is provided for the transmission of a motor drivemovement via one of the two wheels to the strapping band, is reduced atleast to such an extent that slippage or an increased gap can formbetween the band and the wheel pair. If an enlarged gap between thecircumferential surfaces of the wheels is generated in the event of theclamping action being eliminated, said gap should be larger than theband thickness. The clamping action may for example be reduced simply byvirtue of a pressure force with which the two wheels are pressed againstone another being reduced, for example by way of a variably adjustablemagnitude of said pressure force. Such a reduction of the clampingaction may alone be sufficient for a strapping band to be able to movebetween the wheel pairs of its own accord.

The possibility of movement of the strapping band between the wheels ofthe wheel pair may however alternatively also be realized by virtue ofan operative connection between a driven wheel and its drive beingeliminated, such that both wheels of the wheel pair are rotatable freelyand without a holding torque of the drive device. Such an elimination ofan operative connection may be performed for example by way of aswitchable clutch in the drive train of the driven wheel. By way of saidswitchable clutch, it is also possible for the operative connection tobe restored in order for a drive movement, in particular a bandretraction movement, to subsequently be imparted by the driven roller tothe strapping band again.

By way of free rotatability of the wheel pair, or at least slippage oran adequately large gap between the wheels, it is made possible for thestrapping band, immediately after or even during the generation of theband loop, to discharge excess band length of the band loop throughbetween the wheel pair, whereby it is sought to as far as possibleprevent the formation of a convolution. An incipient excess band lengthin the strapping channel leads to buckling in the band loop and thus tocompressive and/or bending stresses in the strapping band. Normalstrapping bands exhibit a flexural rigidity which has the effect thatsuch bands have the tendency to dissipate compressive and bendingstresses by seeking to assume planar and rectilinearly runningorientation. This is advantageously utilized by the present disclosurein that, through the creation of a possibility for movement of the bandthrough between the wheel pair, excess band length can move inparticular of its own accord out of the band channel again between thewheels owing to the self-relaxation of the band.

In another refinement of said further aspect of the present disclosure,a strapping device in the case of which an advancing movement of theband through the strapping device is provided for the formation of aband loop and, here, the band is clamped between a motor-driven rollerand a counterpart roller, a clearance device can be provided. Accordingto this aspect of the present disclosure, in the case of a strappingdevice, the clearance device may be provided for performing aclearance-generating process between the driven roller and itscounterpart roller, by way of which a spacing between the driven rollerand its counterpart roller is generated or enlarged and is subsequentlyreduced in size again. In this context, therefore, the expression“generating a clearance” may be understood to mean the generation of aspacing.

With this measure according to said further aspect of the presentdisclosure, it is possible in a particularly functionally reliablemanner for the formation of a convolution in the band noose or loop, inparticular in the region of a band drive device of the strapping device,such as has hitherto often arisen after the completion of the bandadvancement process in the case of a high band advancement speed and canlead to malfunctions of the strapping device, to be at leastsubstantially avoided. Excess band can move in the direction of the bandstore again of its own accord through the gap, enlarged owing to theclearance-generating process, between the two rollers. Such a backwardmovement of a band section through the enlarged gap between the tworollers may take place automatically, in particular owing to the impetusor the kinetic energy present in the band owing to the band advancementthat has previously taken place and the flexural rigidity of the band,without the need for a corresponding motor-generated drive movement tobe imparted to the band in the same direction.

It is advantageously possible for the clearance-generating processbetween the two rollers to be eliminated again before the bandretraction process effected by motor drive movement, and for the tworollers to be placed in contact with one another again. Theclearance-generating process is thus performed at a time between theband advancement process and the band retraction process. A time overlapbetween the band advancement process and/or the band retraction process,on the one hand, and the clearance-generating process, on the otherhand, is possible here but is not imperative.

In a further expedient embodiment of the present disclosure according tothis aspect, the non-motor-driven counterpart roller may be arranged ona rotatable eccentric. Here, the clearance-generating device may act onthe eccentric in order, by way of rotation of the eccentric and theeccentricity, to generate between the two rollers a gap which is greaterthan the band thickness. After the completion of theclearance-generating process, the eccentric can be rotated in the thenopposite direction again, whereby the two rollers clamp the band betweenthem again and a band retraction process can be performed by way of thetwo rollers. Said embodiment of the present disclosure has inter aliathe advantage that a fast movement of the counterpart roller for thegeneration of a spacing to the driven roller, and an advancing movementtoward the driven roller again, are possible by way of an eccentric witha relatively small structural space requirement. In other embodiments ofthe present disclosure, the spacing between the two rollers for theclearance-generating process may self-evidently also be realized in someother way, for example by way of a pivoting movement or a linearmovement of at least one of the two rollers.

In a further expedient embodiment of the present disclosure, it may beprovided that the clearance-generating movement is realized by way of alinearly movable driven element such as for example a stroke-performingpiston. Such stroke-performing elements are available in a variety offorms and with different drive principles. With such stroke-performingelements, it is possible the drive movement to form particularlyfunctionally reliable clearance-generating devices. Furthermore, withsuch drive elements, it is also possible with relatively little outlayfor existing strapping apparatuses to be retrofitted with aclearance-generating device.

Further embodiments of the present disclosure will emerge from theclaims, from the description and from the drawing. The content ofdisclosure of the patent claims is hereby incorporated by reference intothe description. The present disclosure will be discussed in more detailbelow on the basis of exemplary embodiments which are illustrated purelyschematically in the figures.

FIG. 1 is a highly schematized illustration of a strapping apparatusaccording to the present disclosure which is equipped with a strappinghead according to the present disclosure.

FIG. 2 is a perspective illustration of a strapping head according tothe present disclosure.

FIG. 3 is a perspective illustration from above of the strapping headfrom FIG. 2 integrated into a band guide of a strapping apparatus.

FIG. 4 shows a side view of the strapping head from FIG. 2, in the caseof which a component is situated in a pivoted-out servicing position.

FIG. 5 is a perspective partial illustration of the strapping head fromFIG. 2, with the band drive device being illustrated.

FIG. 6 shows a front view of the band drive device from FIG. 5.

FIG. 7 is a perspective illustration of a tensioning wheel according tothe present disclosure with a partial illustration of the knurling ofthe circumferential surface of the tensioning wheel.

FIG. 8 shows a front view of the tensioning wheel from FIG. 7.

FIG. 9 is a cross-sectional illustration of the tensioning wheel along adiameter line.

FIG. 10 shows a component of a lever mechanism for a counterpart rollerof the band drive device.

FIG. 11 shows a further component of the lever mechanism of thecounterpart roller in a perspective illustration.

FIG. 12 shows the component from FIG. 11 in a front view.

FIG. 13 is a sectional illustration of the component from FIGS. 11 and12.

FIG. 14 is an exploded illustration of another exemplary embodiment of atensioning wheel.

FIG. 15 is a perspective illustration of the tensioning wheel from FIG.14.

FIG. 16 shows a front view of the tensioning wheel from FIGS. 14 and 15.

FIG. 17 is a sectional illustration of the tensioning wheel from FIGS.14-16.

FIG. 18 shows a further exemplary embodiment of a band drive deviceaccording to the present disclosure with a clearance-generating devicein a partial illustration of a strapping head.

FIG. 19 shows the band drive device from FIG. 18 in an illustration inwhich a clearance has been generated between a counterpart roller andthe driven roller that interacts therewith.

FIG. 1 shows a strapping apparatus 1 which is equipped with a controller2, a supply device 3 for storing and making available a strapping band,and with a strapping head 5. The strapping head 5 serves inter alia forthe generation of an advancement movement and for the generation of aretraction movement of the strapping band. Said strapping head isfurthermore equipped with a tensioning device, for imparting a bandtension to a band loop, and a fastening device for generating afastening on the strapping band. Furthermore, the strapping apparatushas a band guide 6 by way of which the band can be mechanically andautomatically laid around a packaged item 7 on a predefined path. Awelding and clamping unit 16 is also integrated into the strapping head5. Aside from the strapping head 5, these are components that are knownper se of strapping apparatuses.

The strapping head 5, which is arranged together with the band guide 6on a frame 8 and which is separately illustrated in FIG. 2 has a banddrive device 15. Band drive devices are basically already known, forwhich reason substantially the differences in relation to previouslyknown band drive devices will be discussed below. The band drive deviceaccording to this exemplary embodiment may be equipped in particularwith one or more roller pairs 11, 12; 13 and possibly with furtherindividual diverting rollers. The latter however do not participate inthe generation of the band movement and are provided only fordetermining the band running direction. Of the three rollers 11, 12, 13in the exemplary embodiment which generate the band movements, at leastone of the rollers 11, 12, 13 should be motor-driven for the purposes ofgenerating a band advancement or band retraction movement. Here, in eachcase one roller 11, 12, 13 of the roller pairs formed from said rollers,between which roller pairs the strapping band is led through and in theprocess an advancement, retraction or tensioning movement, and possiblya tension-relieving movement, is transmitted to the band, should bedriven.

The strapping head 5 has two components: a control component 16 and aband handling component 17. In the exemplary embodiment, the controlcomponent 16, aside from the execution of control functions for thecomponents of the strapping device, has further functions, for examplethe generation of fastenings between the two belt layers of a strap andthe cutting of the strapping band from the band supply. The controlcomponent 16 is in this case mounted on a partial carrier 18 of thestrapping head, wherein the partial carrier 18 is in turn detachablyfastened to a common main carrier 19 of the strapping head 5. As can beseen in particular from FIG. 4, the partial carrier 18 of the controlcomponent 16 is pivotable about an axis 23. The elements of the bandhandling component 17 are fastened, without a dedicated partial carrier,directly to the main carrier 19 of the strapping head. In the exemplaryembodiment, the control component 16 is provided substantially forperforming control and coordination functions out of the functionsperformed by the strapping head. The band handling component 17 and thecomponents attached thereto are, by contrast, provided for actingdirectly on the strapping band.

A band advancement device 20, a band retraction device 21 and atensioning device 22 are integrated into the band handling component 17of the strapping head 5. In the exemplary embodiment shown here, commonrollers 11, 12; 13 are provided for the band advancement, bandretraction and tensioning devices 20, 21, 22. Of the total of only threerollers 11, 12, 13, two rollers 11, 12 are motor-driven rollers. The tworollers 11, 12 are driven by the same (only one) motor 14, in theexemplary embodiment an electric motor. For this purpose, it may forexample be provided that, from the common motor 14, in each case onedrive train leads to one of the two rollers 11, 12. Here, the roller 11is provided both as a drive wheel for the band advancement (bandadvancement wheel) and as a drive wheel for the band retraction (bandretraction wheel). In order that, in the exemplary embodimentillustrated, said two functions can be performed by way of only onewheel, the roller 11 can be driven in both directions of rotation by thesame drive motor 14. Here, in the illustration of FIG. 6, the directionof rotation counterclockwise is the band advancement direction, and thedirection of rotation clockwise is the band retraction direction. Asshown in FIG. 2, the motor drive movement is transmitted to both wheelsor rollers 11, 12 by the common motor 14 by way of a mechanism device.In the present exemplary embodiment, the mechanism device 14 a comprisesa toothed-belt mechanism which transmits the drive movement from themotor shaft to a further shaft running parallel to the motor shaft. Onsaid further shaft there are arranged two gearwheels which belong ineach case to a further one of two partial mechanisms of the mechanismdevice. One of said two partial mechanisms of the mechanism devicetransmits the motor drive movement to the roller or the wheel 11, andthe other partial mechanism transmits the motor drive movement to thetensioning wheel 12. Depending on the direction of rotation of the motorshaft, it is thus the case in the exemplary embodiment that both thetensioning wheel 12 and the wheel 11 rotate in different directions ofrotation.

In the installed position of the strapping head depicted in FIGS. 5 and6, the roller 11 is arranged above the roller 12. The roller 12 is aconstituent part of the tensioning device 22 and has the function of thetensioning wheel. Said roller has a considerably greater diameter thanthe roller 11. The tensioning wheel 12, owing to the rigid connection tothe motor 14 and the drive movements in both directions of rotationperformed by the motor, can likewise be driven in both directions ofrotation. For the imparting of the intended band tension to thestrapping band, in particular to the band loop, the tensioning wheelhowever utilizes only the drive movement in the tensioning direction,that is to say the clockwise direction of rotation as viewed in theillustration of FIG. 6. In certain embodiments, a release of tensionfrom the band section which is situated in the strapping head, and whichis no longer part of the band loop, may be realized by way of arotational movement of the tensioning wheel, taking place after thetensioning process, in the direction of rotation opposite to that duringthe tensioning process. The drive movements both for the tensioningmovement and for the tension-relieving movement originate from the samedrive motor as for the roller 11. As an alternative to the exemplaryembodiment of the present disclosure illustrated here, it is possible inother embodiments for a switchable clutch to be provided in thedrivetrain (not illustrated in any more detail) from the motor to thetwo rollers 11, 12, by way of which clutch the drive movement can beconducted either to the roller 11 or to the roller 12. Aside fromembodiments in which the tensioning wheel is in turn capable of beingdriven in both directions of rotation, it may also be provided that thetensioning wheel can also be driven only in the direction of rotationprovided for the tensioning process.

As can be seen from the illustration of FIG. 6, the roller 13 isadjacent both to the roller 11 and to the tensioning wheel 12. Theroller 13 is not driven in rotation and is pivotably articulated by wayof a pivoting device. The pivoting device is operatively connected to adrive by way of which the roller can perform (motor-) driven pivotingmovements. By way of the pivoting movement, the roller 13 whichfunctions as counterpart roller can be placed either in contact with theroller 11 or in contact with the tensioning wheel 12, wherein, in therespective end position of the pivotable roller 13, the strapping bandis situated in each case between one of the rollers 11, 12 and theroller 13. Depending on which of the rollers 11, 12 the counterpartroller 13 bears against, the counterpart roller 13 then forces the bandagainst the corresponding roller 11, 12 such that the correspondingroller 11, 12 can transmit its rotational movement with the leastpossible slippage as an advancement, retraction or tensioning movement,and possibly as a tension-relieving movement, to the strapping band. Thecounterpart roller 13 is thus, together with the roller 11, both aconstituent part of the band advancement device and a constituent partof the band retraction device. Together with the tensioning wheel 12,the counterpart roller 13 is also a constituent part of the tensioningdevice 22. By way of this configuration according to the presentdisclosure, it is possible for the fourth roller that has hitherto beenconventional in previously known solutions to be dispensed with. In thecase of said previously known solutions, the drive roller and thetensioning wheel are in each case fixedly assigned one of twocounterpart rollers. The 3-roller solution according to the presentdisclosure can permit a considerably more compact embodiment in relationthereto.

The rollers 11, 12, 13 are, in the strapping head 5, furthermore aconstituent part of a band guide channel 28 which predefines the profileand the advancement and retraction path of the band. The band guidechannel 28 is in turn part of the band guide 6. As can be seen in FIG.6, the strapping head 5 has a first interface 29 at which the strappinghead 5 adjoins the supply roll side of the band guide. That end of theband guide channel 28 which is formed here is in the form of aquick-change interface. This has a channel piece 31 which can be clampedto the strapping head by way of a pivotable clamping lever 30 andthrough which the band is supplied into the strapping head. The channelpiece 31 ends directly in front of the circumferential surface 11 a ofthe roller 11, such that the strapping band can be supplied at leastapproximately tangentially to the circumferential surface 11 a of theroller 11. If the roller 13 is situated in its end position in which itis pivoted toward the roller 11, the band is led through between therollers 11, 13, wherein the roller 13 forces the band against the roller11.

As viewed in the band advancement direction 32, the band passes, in itsfurther progression, to the tensioning wheel 12. Here, proceeding fromthe counterpart roller 13, a circular-arc-shaped channel section 28 awhich extends over approximately 180° of the circumference of thetensioning wheel 12 is formed by way of suitable channel-forming means.With regard to the band thickness, the channel section 28 a is formed soas to be considerably wider than the band thickness. The innerdelimitation of the channel section is formed by that section of thecircumferential surface 12 a of the tensioning wheel 12 which issituated in each case in the region of the channel section. The outerdelimitation of the channel section 28 a as viewed radially has guideplates and an outer channel segment which is pivotable together with thecounterpart roller 13, by way of which outer channel segment the outerchannel section can be kept closed despite the pivotable counterpartroller 13 being situated in the region of the outer channel section.Without the pivotable channel segment 33 or some other element ofsimilar action, there would possibly be an open point of the channelsection at least in one of the two pivoting end positions of thecounterpart roller 13, which open point could possibly have an adverseeffect with regard to reliable band guidance.

FIGS. 7, 8 and 9 show the tensioning wheel in three illustrations. Saidtensioning wheel has a ring 37 which is equipped with a recess 38 whichis provided for the connection of the tensioning wheel 12 to a shaft ofthe drive, in particular to a shaft of a mechanism of the drive. FIG. 2shows the tensioning wheel 12 mounted on the shaft. As can likewise beseen from FIG. 6, the circular tensioning wheel has a circumferentialsurface 12 a with an at least substantially constant width. Thetensioning wheel 12 is equipped, on its circumferential surface 12 a,with a knurling or toothing 39 by way of which the engagement conditionsof the tensioning wheel 12 on the strapping band are improved. Insteadof a knurling or toothing 39, it would also be possible for any othergeometrically defined or undefined roughening of the circumferentialsurface 12 a of the tensioning wheel to be provided, by way of whichpossible slippage between the tensioning wheel and the strapping bandduring the tensioning process can be at least substantially prevented.

A groove 40 with a relatively small width is formed over the entirecircumference of the circumferential surface 12 a at least approximatelycentrally—in relation to the width of the tensioning wheel 12—and so asto be spaced apart from the lateral edges of the tensioning wheel, whichgroove is formed so as to be considerably deeper than it is wide. In theexemplary embodiment, two resiliently elastic O-rings 43, 44 aresituated one above the other in the groove 40, said O-rings beingarranged radially one behind the other in the groove 40. Here, one ofthe O-rings 43 is arranged with a relatively small spacing to the axisof rotation of the tensioning wheel 12, and the other O-ring 44 isarranged with a relatively large spacing to the axis of rotation of thetensioning wheel 12. The width of the O-rings 43, 44 is in this caseprovided so as to approximately correspond to the width of the groove40. The two O-rings 43, 44 are situated entirely within the groove 40.The two O-rings 43, 44 are formed from resiliently elastic material.

On the outer of the two O-rings 43, 44 there is seated a ring 45 whichis provided as a spacer element and which, in the exemplary embodiment,is formed from a metallic material. In this exemplary embodiment, thering 45 is elastically deformable. It would likewise be possible for thering to be of substantially rigid or dimensionally stable form. Torealize said elastic characteristics of the ring, it would also bepossible for the ring 45 to be formed from one or more materials otherthan a metallic material, for example from an elastic plastic. In theexemplary embodiment, said metal ring 45 is, in terms of its crosssection, provided so as to have a width B smaller than its height H. Theheight of the O-ring is, with regard to the groove depth and the heightof the O-rings, configured such that the ring projects with a height H₁out of the groove 40. Thus, in its unloaded state shown in FIG. 9, thering 45 projects beyond the circumferential surface 12 a of thetensioning ring 12, in particular over its entire circumference or overthe entire circumference of the tensioning ring 12.

At the start of the strapping process, the strapping band is pushed athigh speed, with its free band end first, from the strapping head 5through the band guide 6. For this purpose, the counterpart roller 13 isin contact with one side of the band. The band is forced with its otherside against the motor-driven roller 11 by the counterpart roller. Therotational drive movement of the roller 11 in the advancement directionis in this way transmitted to the strapping band, which effects theadvancement movement thereof in the advancement direction. Downstream ofthe region in which the band emerges from the gap between roller 11 andcounterpart roller 13, the band comes into contact with the tensioningwheel 12, but without exerting a significant pressure on the tensioningwheel 12.

After the band has been pushed all the way through the band guide 6, theband end reaches the closure head again. Here, the band end actuates alimit switch, whereby the advancement movement is stopped and the bandend is clamped. These and other activation and deactivation processes ofcomponents of the closure head are performed by the control component 16which, for this purpose, is equipped with a motor-driven camshaftcontrol arrangement such as is basically known.

The camshaft control arrangement of the control component 16 now setsthe roller 11 in motion in a direction of rotation reversed in relationto the advancement direction. The strapping band, which remains clampedbetween the roller 11 and the counterpart roller 13, is hereby moved inthe reverse direction, that is to say in the band retraction direction48. The circumferential length of the band loop, the band end of whichremains clamped, is hereby continuously shortened. The band is herebypulled out of the band guide 6 and, as a result, laid around therespective packaged item.

FIG. 6 illustrates the tensioning wheel 12 during the band retractionprocess. As can be seen from said illustration, it is the case duringthe band retraction process that the band comes into contact with thetensioning wheel 12. The strapping band bears against the tensioningwheel 12 substantially over the entire circular-arc-shaped channelsection 28 a, similarly to the situation also encountered during thesubsequent tensioning process. The band is duly retracted here, but,owing to its ability to yield to said movement by moving, as intended,out of the band guide, it is nevertheless the case during said phasethat only a relatively low band tension is applied to the band of theband loop. As a result of said contact with the tensioning wheel 12 andof the ring 45 which projects in relation to the circumferentialsurface, the band bears not against the circumferential surface of thetensioning wheel 12 but against the ring 45 situated in thecircumferential surface 12 a. Said contact with the spacer element,which, in the exemplary embodiment, is in this case in the form of aring 45, has the effect that, during the band retraction, the bandcannot be damaged by the knurling or toothing 39 of the circumferentialsurface 12 a.

After the band has been laid against the packaged article as a result ofthe band retraction, the controller switches from band retraction togeneration of a band tension, whereby it is the intention for the bandlaid against the packaged article to be pulled taut. For this purpose,it is firstly the case that the counterpart roller 13 is pivoted fromits position of contact against the roller 11 into a position of contactagainst the tensioning wheel 12. The tensioning wheel 12, which isrotated in the same direction of rotation as the roller 11 waspreviously, rotates at a lower rotational speed but with a greatertorque, and pulls further on the strapping band. Owing to the absence ofpressure of the counterpart roller 13, it is by contrast now the casethat the band no longer bears against the roller 11, which continues tobe driven in the exemplary embodiment and which rotates at a higherspeed, in such a way that the roller 11 could transmit its movement tothe band. Since, at this stage, the strapping band already bears againstthe packaged article, the band is, by the tensioning wheel 12, retractedat most over a short length in relation to the band retraction phase.During said tensioning phase, it is in particular the case that arelatively high band tension is applied to the band.

Already at the start of the tensioning phase, the pressure of thecounterpart roller 13 in the direction of the tensioning wheel and theband situated in between causes the ring 45 to be forced in thedirection of the groove base and thus also in the direction of the axisof rotation of the tensioning wheel 12 as viewed in a substantiallyradial direction. In this way, it is the case already at the start ofthe tensioning phase that the band bears against the ring 45 and forcesthe latter likewise, at least in the region of the counterpart roller13, in the direction of the groove base. Thus, already at the start ofthe tensioning process, the ring 45 has, in the region of thecounterpart roller 13, a smaller spacing to the axis of rotation of thetensioning wheel than in its unloaded state, for example during the bandadvancement or the band retraction phase.

The torque transmitted from the tensioning wheel 12 to the band duringthe further course of the tensioning process, which torque is higherthan that in the band retraction phase of the roller 11, results in agreater reaction force of the band. Said greater reaction force now hasthe effect that the band forces the ring 45 into the groove not only inthe contact region with the counterpart roller 13 but over its contactlength (wrap angle as viewed in the circumferential direction) with thering 45, whereby the band now bears, along its wrap angle on thetensioning wheel 12, against the circumferential surface of saidtensioning wheel. Along its wrap angle on the tensioning wheel, the bandforces the ring into the groove counter to the spring forces of theO-rings. Depending on the characteristics of the ring 45, said ring isdeformed possibly elastically as a result, and, along thatcircumferential section in which the strapping band does not bearagainst the tensioning wheel, said ring can partially (with regard toits height) emerge from the groove again. Outside the wrap angle of theband on the tensioning wheel, the ring 45 may in this case project outof the circumferential surface to a greater extent than in the unloadedstate, in the case of which it projects with a height H. Since the ringis arranged rotationally conjointly in the groove, it is the case, in amanner dependent on the respective rotational position of the tensioningwheel 12, that each individual point of the ring is forced into thegroove 40, and emerges from said groove again, in alternating fashionuntil, owing to the rotation of the tensioning wheel, said point arrivesagain at the point at which the band wraps around a section of thecircumferential surface and thereby forces the ring into the groovealong said section. It is thus possible, despite the means provided forpreventing the strapping band from coming into contact with thecircumferential surface of the tensioning wheel during the bandretraction phase, for functionally reliable contact of the band with thesame tensioning wheel to nevertheless be achieved during the bandtensioning phase.

The counterpart roller 13 can advantageously be forced with differentpressing forces firstly against the roller 11 (advancement roller orretraction roller) and secondly against the tensioning wheel 12 (duringthe use of the strapping device in each case with a strapping bandsituated in between). Higher pressing forces against the tensioningwheel than the possible pressing forces against the roller 11 can beadvantageous for high functional reliability and for the possibility ofapplying high band tensions to the strapping band. Therefore, below, itwill be discussed how, in one embodiment of the present disclosure,despite the pivoting movement of the counterpart roller 13 between twoend positions, different pressing forces can be realized in the endposition.

For this purpose, the counterpart roller 13 is arranged on an eccentric50 which, in turn, is arranged on a shaft 51 of a carrier 52. Thecarrier has, spaced apart from the shaft 52, a receptacle 53 which isprovided for arrangement on the bearing point 54 of the roller 11 (FIGS.5 and 6). Here, the receptacle 53 is freely rotatable about its axis ofrotation on the bearing point 54 of the roller 11 and can thus performpivoting movements about its axis of rotation.

In the region of the counterpart roller 13 and of the roller 11, thereis provided a parallelogram which has multiple levers 57, 58, 59 whichare pivotably articulated on one another. The parallelogram 56 has along vertical lever 57, a horizontal lever 58 and a short vertical lever59. The parallelogram is pivotably articulated on the long verticallever 57 and on the short vertical lever 59. The levers 57 and 59 havepivot bearing points 60, 61 for this purpose. Via a bell-shaped curve62, it is possible for a rotational movement to be transmitted to thelong vertical lever 57, which rotational movement leads to the pivotingmovement of the lever 57 about its pivot bearing point 60. In theillustration of FIG. 12, the pivoting movement of the lever 57 takesplace clockwise.

In this way, at the articulation point of the short vertical lever, thelever 58 also pulls said short vertical lever in the direction of thelever 57, whereby the vertical lever 59 is, in the illustration of FIGS.11 and 12, likewise pivoted clockwise about its pivot bearing point 62.As a result, an oblique surface 64 formed on the short vertical lever 59pushes against a bearing 51 arranged on the shaft 51. As a result, theoblique surface performs a movement clockwise (in the illustration ofFIG. 12) and has the tendency to assume a horizontal orientation. As aresult, the carrier 52 performs a pivoting movement, whereby thecounterpart roller 13 is pivoted from its end position against theroller 11 in the direction of the tensioning wheel 12.

When it reaches the tensioning wheel, the counterpart roller bearsagainst the tensioning wheel and can perform no further pivotingmovement. The lever 57 however pivots further, whereby the bearing point65 of the eccentric 50 is moved counterclockwise in the direction of anL-shaped carrier 66. After the bearing point 65 pushes against theL-shaped carrier 65, the movement of the bearing point 65 stops, andsaid bearing point is situated at least approximately in a line with anupper bearing point 66, the axis of rotation 67 of the counterpartroller 13 and the axis of rotation 68 of the tensioning wheel 12. Aspring element that has hitherto generated the pressing force of thecounterpart roller 13 is, as a result, no longer active.

A further movement of the lever 57 during its pivoting movement now hasthe effect that the lever 59 can also perform no further movement, andtherefore two parts 58 a and 58 b of the horizontal lever 58 are pulledapart. A spring element 70 arranged between the two parts 58 a, 58 b ofthe lever is hereby compressed, whereby the spring force thereofincreases. This leads to a torque of the lever 59 about the pivotbearing point 61 with the lever arm of the spacing of the pivot bearingpoint 61 from the articulation point 71 of the lever 58 on the lever 59.As a result, the oblique surface 64 pushes, in the form of a torqueabout the pivot bearing point 61, against the bearing, which now leadsto a pressing force of the roller 13 against the tensioning wheel. Byway of a correspondingly dimensioned and designed spring element 70 andcorresponding lever ratios, it is possible in this way to realize highpressing forces of the roller 13 against the tensioning wheel.

A restoration of the parallelogram can be realized by way of a furtherspring 73 arranged on the peg 72 of the lever 5.

Alternative embodiments of components and assemblies discussed abovewill be described below. Here, substantially only differences inrelation to the corresponding components from FIGS. 1 to 13 will bediscussed. Where said embodiments include identical or similarconfigurations to those in the exemplary embodiment of FIGS. 1 to 13,these will not be discussed in any more detail below; the content ofdisclosure of the exemplary embodiments of FIGS. 1 to 13 is however alsoincorporated by reference for the exemplary embodiments of FIGS. 14 to19.

FIGS. 14, 15, 16 and 17 illustrate a further embodiment of a tensioningwheel 112 according to the present disclosure. The tensioning wheel 112may be divided longitudinally in terms of its width, approximately inthe center, wherein the two parts 112 b, 112 c of the tensioning wheel112 are detachably connectable to one another by way of suitablefastening elements, for example screws 114. In the region of saidparting plane, which need not run in a flat manner, an encircling groove140 is formed in the outer ring 137 of the tensioning wheel 112, whichgroove is open toward the circumferential surface 112 a of thetensioning wheel 112 and is narrowed or decreased in size toward saidcircumferential surface.

One or more restoring elements may be arranged in the groove 140. In theexemplary embodiment, as a restoring element, there are arranged elasticring sections 143, for example multiple resiliently elastic O-ringsections 143. Said ring sections are distributed in the groove 140 atregular intervals with respect to one another, as is the case in theexemplary embodiment with a total of four ring sections 143. Therestoring elements 143 are situated below one or more spacer elements.In the exemplary embodiment, only one spacer element 145, in the form ofa closed ring, is provided. An outer diameter of the ring 145 arrangedin the groove is in this case dimensioned such that, in the unloadedstate of the ring 145, said ring projects with its outer circumferentialsurface beyond the circumferential surface 112 a of the tensioning ring112. The ring 145 is situated with its inner circumferential surface inthe groove. The restoring elements are attached to the innercircumferential surface of the circular and substantially dimensionallystable ring 145. In other embodiments, it is also possible for adifferent number of spacer elements, and a different number of restoringelements, to be provided.

As a result of contact of the strapping band against the ring 145, andas a result of a certain minimum pressure force being exerted on thering along a certain angle range along a section of the circumference ofthe tensioning wheel by the strapping band, it is possible forapproximately that section of the ring 145 which projects beyond thegroove along said angle range to be forced into the groove 140, suchthat, in said positionally static angle range of the tensioning wheel112, the strapping band comes into contact with the circumferentialsurface 112 a of the tensioning wheel 112 and can be driven along by thecircumferential surface 112 a during the movement of the tensioningwheel 112. The ring 145, which substantially cannot be deformed by theexpected forces acting thereon in the exemplary embodiment, and which isthus dimensionally stable, is thus arranged slightly eccentrically inrelation to the axis of rotation of the tensioning wheel during saidprocess. The ring 145 hereby projects, with its section not encompassedby the wrap angle of the band, out of the groove 140 further than whenthe tensioning wheel is in the state in which it is not subject to loadby the strapping band. As a result of the ring 145 being relieved of theload of the strapping band, or when a pressure force exerted on the ring145 by the strapping band is not sufficient, it is possible, after thecompletion of the tensioning process, for the elastic restoring forcesof one or more of the ring sections 143 to cause the ring 145 to projectout of the groove again over its entire circumference.

By way of this arrangement, it is possible, during the tensioningprocess, during which the tensioning band exerts an adequately highpressure force on the ring 145 situated in the wrap region of thestrapping band, for the ring 145 to be forced in sections into thegroove 140. During the retraction process, during which only arelatively low tensile stress is present in the strapping band, thepressure force on that section of the ring 145 which is presentlyarranged in the wrap region of the band is not high enough to force saidring section entirely into the groove 140. As a result, the band bearsagainst the section of the ring 145 and not against the surface of thetensioning wheel 112. The ring 145 holds the strapping band so as to bespaced apart from the circumferential surface of the tensioning wheel112.

FIGS. 18 and 19 illustrate a further exemplary embodiment of a banddrive device 115. Said band drive device also has only three rollers111, 112, 113 which are responsible for imparting the band advancement,band retraction and band tensioning movements to the band by way ofcontact with the band, wherein the two rollers 111 and 112 can be drivenby way of a motor, in particular by way of only one common motor. Therelative arrangement of the axes of rotation of the three rollers 111,112, 113 with respect to one another corresponds at least approximatelyto the arrangement of said axes of rotation in the exemplary embodimentof FIGS. 5 and 6.

The counterpart roller 113 is again designed to be pivotable, such that,in one pivoting position, it is provided for pressing the strapping bandagainst the roller 111, and in another pivoting position, it is providedfor pressing the strapping band against the tensioning roller 112. Thepivoting mechanism, provided for this purpose, of the counterpart roller113, and the drive of said pivoting mechanism, may in principle be ofthe same design as in the exemplary embodiment of FIGS. 1 to 13. As inthe exemplary embodiment of FIGS. 5 and 6, the counterpart roller 113 isrotatably mounted on an eccentric 150, such that the counterpart roller113 performs a non-circular-arc-shaped movement during a pivotingmovement from one of the rollers 111, 112 to the respective other roller111, 112. As shown in FIGS. 18 and 19, a clearance-generating device 180is mounted on the eccentric 150 of the counterpart roller 113, whereinthe clearance-generating device 180 is supported with a carrier 181 onthe frame of the strapping apparatus 101. The bearing point 182 of theclearance-generating device on the eccentric 150 is itself arrangedpivotably on the eccentric, and is in the form of a C-shaped orfork-shaped element 183 to thereby form a receptacle for one end of apiston 184. Said piston 184 is arranged in displaceable fashion in thecarrier 181 of the clearance-generating device 180. In the illustrationof FIGS. 18 and 19, the support point is situated immediately above theroller 111. The carrier 181 of the clearance-generating device is inthis case likewise mounted in pivotable fashion.

In the exemplary embodiment shown, the clearance-generating device 180is equipped with a clearance-generating element which is provided forperforming a controlled movement by way of which the counterpart roller113 is acted on in order for the counterpart roller 113, in its pivotededition against the roller 111, to be moved such that a clearance isgenerated, or to be lifted slightly. The counterpart roller 113, in itspivoted position at the roller 111, should, even after the generation ofa clearance, be able to be placed against the roller 111 again, forexample likewise by way of the clearance-generating device. In theexemplary embodiment, the clearance-generating element is in the form ofa solenoid 186 which is arranged and mounted on the clearance-generatingdevice 180. The solenoid 186 can, by way of its piston 184, perform alinear stroke movement along the longitudinal axis 184 a of its piston184. As shown in FIGS. 18 and 19, one end of the piston 184 is arrangedin the recess, which is open toward the carrier 181, of the C-shaped orfork-shaped element 183. The end of the piston 184 and the recess of theC-shaped element may in this case be designed such that, during theclearance-generating movement, the end of the piston 184 in the C-shapedelement can move relative thereto.

Here, the extended longitudinal axis 184 a of the piston 184 runs atleast approximately through the articulation point of the C-shapedelement 183. A stroke movement of the piston 184 in the direction of thecounterpart roller 113 thus leads to a rotational movement of theeccentric about its axis of rotation. In the illustration of FIG. 18,the rotational movement takes place counterclockwise, as can be seenfrom a comparison of the two FIGS. 18 and 19. The rotational movement ofthe eccentric 150 in turn has the effect that the axis of rotation ofthe counterpart roller 113 is displaced in parallel and a gap, or anenlarged gap, is formed between the roller 111 and the counterpartroller 113. The width of the gap should in this case have a size greaterthan the thickness of the strapping band being processed in each case.As a solenoid, use may for example be made of the product GKb-32.06 fromthe company Isliker Magnete AG, CH-8450 Andelfingen.

On the piston 184 there may be arranged a mechanical spring element, inparticular at least one compression spring 188. Said compression spring188 is compressed, and thus braced in resiliently elastic fashion,during the movement of the counterpart roller 113 from the tensioningroller 112 into contact with the roller 111. The electrically actuablemagnetic stroke-performing piston is deactivated, and thus has noaction, in this phase. During the stroke movement, the compressionspring 188 is at least partially relaxed and the spring force acts so asto assist the force imparted by the solenoid, by way of which force thepiston 184 is moved so as to generate a clearance between thecounterpart roller 113 and the roller 111. In other exemplaryembodiments, in which the solenoid or some other restoring element aloneprovides a force high enough for the clearance-generating process.

During the production of the strap, it is the case—as alreadydescribed—that, by way of the roller 111 and the counterpart roller 113which bears against the former roller and clamps the band between thetwo rollers, the band is moved through the band guide channel 28 in afeed direction. When the strapping band reaches the region of the end ofthe band guide channel, as is illustrated by way of example in highlyschematized form in FIG. 1, the band strikes a stop, or the fact thatthe end of the band guide channel has been reached may be detected insome other way, for example by way of a light barrier. In this way, asignal is generated, by way of which the control of the strappingapparatus stops the motor drive movement of the roller 111 and—at leastsubstantially at the same time—triggers the stroke movement of thepiston 184 of the solenoid. In other embodiments of the presentdisclosure, it is also conceivable for the stoppage of the drivemovement of the roller 111 and the start of the clearance-generatingprocess to have a time offset with respect to one another, that is tosay for the stoppage of the drive movement to be performed before orafter the start of the clearance-generating process.

As a result of the starting of the clearance-generating process, thepiston 184 deploys in the direction of the C-shaped element 183 and,here, acts by way of its end on the C-shaped or fork-shaped element.Owing to its arrangement on the eccentric 150, the eccentric is rotatedduring the stroke movement of the piston. In the exemplary embodimentand in the illustration of FIG. 18, the rotational movement of theeccentric takes place through a rotational angle of less than 90°counterclockwise. The rotational movement takes place counter to thespring force of the pressure-exerting spring 190, which in this case iscompressed and is likewise articulated on the eccentric 150. As a resultof the rotational movement, a clearance is generated between thecounterpart roller 113 and the roller 111, that is to say thecounterpart roller 113 is lifted from the roller 111, and the spacingbetween the two rollers 111, 113 is enlarged such that a gap formsbetween the rollers, which gap is larger than the band thickness.

In the case of generic strapping apparatuses, the strapping band, whichis shot at high speed through the band channel of the band guide 6, hasthe tendency, owing to the sudden and abrupt stoppage of the band, toform convolutions between the rollers 111, 112, 113 and the end of thestrapping channel. In particular in the region of the rollers 111, 112,113, such convolutions can lead to malfunctions. Owing to the embodimentaccording to the present disclosure, in which a clearance of thecounterpart roller 113 is generated, the band can, in particularimmediately after the stoppage of the advancement, move freely counterto the advancement direction in the direction of the band supply to theextent required for that part of the band which is possibly excess inrelation to the length of the band channel, and which causes theformation of convolutions, to move back in the band guide channel. Thecontroller of the strapping apparatus can then subsequently deactivatethe solenoid again. As a result, the solenoid is rendered inactive,whereby the pressure-exerting spring 190 can move the eccentric 150 backagain counter to the previous direction of rotation, and thus move thecounterpart roller 113 into its position of contact with the band again,in which the band is clamped between the roller 111 and the counterpartroller 113. The subsequent band retraction and tensioning process can beperformed in the same way as in the embodiments of the presentdisclosure as per FIGS. 1 to 13.

List of reference designations  1 Strapping apparatus  2 Controller  3Supply device  5 Strapping head  6 Band guide  8 Frame  11 Roller  11aCircumferential surface  12 Tensioning wheel  12a Circumferentialsurface of tensioning wheel  13 Counterpart roller  14 Motor  14aMechanism device  15 Band drive device  16 Control component  17 Bandhandling component  18 Partial carrier  19 Main carrier  20 Bandadvancement device  21 Band retraction device  22 Tensioning device  23Axle  27 Pivoting device  28 Band guide channel  28a Channel section 28b Outer delimitation  29 Interface  30 Clamping lever  31 Channelpiece  32 Band advancement direction  33 Outer channel segment  37 Ring 38 Recess  39 Knurling/toothing  40 Groove  43 O-ring  44 O-ring  45Ring  48 Band retraction direction  50 Eccentric  51 Shaft  52 Carrier 53 Receptacle  54 Bearing point  56 Parallelogram  57 Long verticallever  58 Horizontal lever  59 Short vertical lever  60 Pivot bearingpoint  61 Pivot bearing point  64 Oblique surface  65 Bearing point  66Carrier  67 Rotary axle  68 Rotary axle  70 Spring element  71Articulation point  72 Peg 101 Strapping apparatus 111 Roller 112Tensioning wheel 112a Circumferential surface 112b Part 112c Part 113Counterpart roller 114 Screw 115 Band drive device 137 Ring 140 Groove143 Ring section 145 Ring 150 Eccentric 180 Clearance device 181 Carrier182 Bearing point 183 C-shaped element 184 Piston 184a Axis 186 Solenoid188 Compression spring 190 Pressure-exerting spring B Width H Height H₁Height

1-21. (canceled)
 22. A tensioning device for an apparatus for strappingpackaged articles with a strapping band, the tensioning devicecomprising: a tensioning wheel operatively connectable to a drive deviceto rotate the tensioning wheel about an axis of rotation, the tensioningwheel having a circumferential surface configured to engage thestrapping band; and a spacer element mounted on the tensioning wheelsuch that the spacer element is movable between: (1) a first position inwhich at least part of the spacer element has a first spacing from theaxis of rotation and projects beyond the circumferential surface of thetensioning wheel; and (2) a second position in which the at least partof the spacer element has a second spacing from the axis of rotation,wherein the second position is different from the first position and thesecond spacing is different from the first spacing.
 23. The tensioningdevice of claim 22, wherein when in the second position, the at leastpart of the spacer element is substantially flush with thecircumferential surface of the tensioning wheel.
 24. The tensioningdevice of claim 22, wherein the spacer element is movable from the firstposition to the second position via application of force to the at leastpart of the spacer element.
 25. The tensioning device of claim 22,wherein the spacer element is coaxial with the tensioning wheel androtatable with the tensioning wheel.
 26. The tensioning device of claim22, wherein the spacer element is oriented with a longitudinal extent atleast substantially parallel to the circumferential direction of thecircumferential surface.
 27. The tensioning device of claim 22, whereinthe spacer element is disposed in a groove defined in thecircumferential surface.
 28. The tensioning device of claim 27, whereinthe groove extends over at least part of the circumferential surface andthe spacer element includes at least part of a ring.
 29. The tensioningdevice of claim 27, which includes a resiliently elastic elementdisposed in the groove and against which the spacer element bears. 30.The tensioning device of claim 27, wherein the tensioning wheel and thespacer element are positioned and arranged such that, during thetensioning process, the tensioning wheel rotates and, in relation to apositionally static polar coordinate system of the tensioning wheel, thestrapping band forces the spacer element into the groove at least at thesubstantially always identical circumferential section of the tensioningwheel, whereas, at the remaining circumferential section against whichthe strapping band does not bear, the spacer element projects from thecircumferential surface.
 31. The tensioning device of claim 22, whereinthe spacer element is positioned approximately centrally in relation tothe width of the circumferential surface of the tensioning wheel.
 32. Astrapping device for strapping packaged articles with a strapping band,the strapping device comprising: a tensioning device comprising: (a) atensioning wheel operatively connectable to a drive device to rotate thetensioning wheel about an axis of rotation, the tensioning wheel havinga circumferential surface configured to engage the strapping band; and(b) a spacer element mounted on the tensioning wheel such that thespacer element is movable between: (1) a first position in which atleast part of the spacer element has a first spacing from the axis ofrotation and projects beyond the circumferential surface of thetensioning wheel; and (2) a second position in which the at least partof the spacer element has a second spacing from the axis of rotation,wherein the second position is different from the first position and thesecond spacing is different from the first spacing; and a fasteningdevice configured to join two sections of the strapping band.
 33. Thestrapping device of claim 32, wherein during a tensioning process, thestrapping band exerts a first force on the spacer element to cause thespacer element to move from the first position to the second positionsuch that the at least part of the spacer element is substantially flushwith the circumferential surface of the tensioning wheel and thestrapping band contacts the circumferential surface of the tensioningwheel, and wherein during a band retraction process, the strapping bandexerts a second force on the spacer element, the second force being lessthan the first force and insufficient to cause the spacer element tomove from the first position to the second position.
 34. The strappingdevice of claim 32, which includes a band advancement/retraction roller,a counterpart roller, and a motor operably connected to the bandadvancement/retraction roller to drive the band advancement/retractionroller in two different directions of rotation and also operablyconnected to the tensioning wheel to drive the tensioning wheel in atleast one of the directions of rotation, wherein the counterpart rolleris movable between a first position in which the counterpart rollercontacts the band advancement/retraction roller and a second position inwhich the counterpart roller contacts the tensioning wheel.
 35. Thestrapping device of claim 34, wherein the motor is the only motoroperably connected to both the tensioning wheel and the bandadvancement/retraction roller.
 36. The strapping device of claim 32,which includes a clearance device configured to increase spacing betweena counterpart roller and a motor-driven roller provided for imparting aband movement.
 37. The strapping device of claim 36, wherein theincreased spacing is greater than a thickness of the strapping band. 38.A strapping device for strapping packaged articles with a strappingband, the strapping device comprising: a tensioning device comprising:(a) a tensioning wheel operatively connectable to a drive device torotate the tensioning wheel about an axis of rotation, the tensioningwheel having a circumferential surface configured to engage thestrapping band; and (b) a spacer element mounted on the tensioning wheelsuch that the spacer element is movable between: (1) a first position inwhich at least part of the spacer element has a first spacing from theaxis of rotation and projects beyond the circumferential surface of thetensioning wheel; and (2) a second position in which the at least partof the spacer element has a second spacing from the axis of rotation,wherein the second position is different from the first position and thesecond spacing is different from the first spacing; a fastening deviceconfigured to join two sections of the strapping band; and an encirclingstrapping channel configured to guide the strapping band during astrapping process.
 39. The strapping device of claim 38, wherein duringa tensioning process, the strapping band exerts a first force on thespacer element to cause the spacer element to move from the firstposition to the second position such that the at least part of thespacer element is substantially flush with the circumferential surfaceof the tensioning wheel and the strapping band contacts thecircumferential surface of the tensioning wheel, and wherein during aband retraction process, the strapping band exerts a second force on thespacer element, the second force being less than the first force andinsufficient to cause the spacer element to move from the first positionto the second position.
 40. The strapping device of claim 38, whichincludes a band advancement/retraction roller, a counterpart roller, anda motor operably connected to the band advancement/retraction roller todrive the band advancement/retraction roller in two different directionsof rotation and also operably connected to the tensioning wheel to drivethe tensioning wheel in at least one of the directions of rotation,wherein the counterpart roller is movable between a first position inwhich the counterpart roller contacts the band advancement/retractionroller and a second position in which the counterpart roller contactsthe tensioning wheel.
 41. The strapping device of claim 38, whichincludes a clearance device configured to increase spacing between acounterpart roller and a motor-driven roller provided for imparting aband movement.